1. Field of the Invention
The present invention relates to an optical projector apparatus; more specifically, it relates to a projector apparatus with multi-light sources and a light coupling module thereof.
2. Descriptions of the Related Art
Nowadays, projector apparatus products, such as digital light processing (DLP) projector apparatuses, liquid crystal display (LCD) projector apparatuses, and liquid crystal on silicon (LCOS) projector apparatuses, are diversified for different customers. For example, in the popular DLP projector apparatus, a micro-electro-mechanical system (MEMS) which adopts a digital micromirror device (DMD) developed by Texas Instruments (TI) to serve as a technical base. In general, the DLP projector apparatus follows these imaging principles: (1) when a light projects from a light source, it travels through a color wheel and then proceeds with a color separation procedure. This procedure could divide light into plural colors and then enters through a light tunnel in optical engine to form a uniformed light; (2) thereafter, DMD receives image input signals which can drive micromirrors of DMD rotating to project correct light and images onto the projection lens; (3) finally, images will be displayed onto a screen along the projecting direction of the projection lens. In comparison to other projector apparatuses that are created using other principles, DLP projector apparatuses have advantages including high brightness quality, color reproducibility, contrast, and small size.
Because the DLP projector apparatus has excellent image presentation, many manufacturers have tried to develop the DLP projector apparatus and its accessories to achieve perfect projection quality. Generally speaking, the DLP projector apparatus should meet requirements that include high brightness quality and large scale projection while presenting images. As a result, it is essential to adopt a light coupling system with dual light sources in the DLP projector apparatus to enhance its image brightness.
As mentioned above (referring to FIG. 1), in a typical optical engine structure with a single light source, a light beam projects from a light source 11 and enters into a light tunnel 14 after its color is separated by the color wheel 15. The color separated light beam is homogenized and transmitted to a rear end of the optical engine 10, by processing the optical engine 10. In the end, an image is projected along a projection direction 17 by a projection lens 16. It is noted that the light beam which travels through the color wheel 15 needs to be a single light beam for color separation.
As mentioned above, in FIG. 2, the two light beams provided by the two light sources 11, 12 must be coupled into a single light beam using a proper light coupling mechanism. Only then would the coupled single light beam be able to travel through the color wheel and enter the single light tunnel. Otherwise, a plurality of light tunnels is necessary to receive a plurality of different light beams provided by different light sources. Under the latter circumstances, the color separation procedure cannot be performed before the light beam is homogenized by the light tunnel because the light beams have not been coupled yet. Thus, in considering the configuration of the above-mentioned elements, the color wheel must be disposed at the rear of the light tunnel so that the light beam is able to enter the light tunnel first. Then, the color separation procedure can follow after the homogenized lights are coupled by some mechanism. However, the single light source structure, shown in FIG. 1, can not share the optical engine 10 with the dual light sources structure, shown in FIG. 2, because the relative positions between the light tunnel 14 and the color wheel 15 are different in these two cases.
Using a prism 13 as another example of the adoption of dual light sources 11, 12 structure, after the dual light beams travel through the prism 13, the beams would approximately couple into a single light beam and travel first through the color wheel and then through the light tunnel. In this case, these light beams from the dual light sources 11, 12 have to travel very closely to the vertex 131 of the prism 13, and accordingly, the prism 13 must be adjusted outwardly by a distance if the light sources do not move inwardly. In addition, the single light beam must run across a space which is used to dispose the color wheel 15 before actually reaching it. The intensity of the light beam is decayed first when coupling, and even worse, the distance across that space may cause a further decrease of the intensity. That is, the light coupling efficiency decreases and image brightness and color are adversely affected as well.
In DLP projector apparatuses, elliptic lamps usually serve as the light sources 11, 12 in a dual light projection system, as shown in FIG. 3A. The two opposite elliptic lamps build up a hypothetic connection line between the centers (normally where the bulbs thereof resides), in which the hypothetic connection line is substantially parallel to the projection direction 17 (i.e. y axis) of the projection lens 16. Referring to FIG. 3B, the elliptic lamps, generally adopted by the industry, create a high temperature region (assuming the area encompassed as reference numeral 18) due to the heat generated by the blaze of the lamps 11, 12. The high temperature region 18 then gradually arises to a top portion between the two electrodes as a result of the upwards rising heat under buoyancy efficiency. To assure a normal service life for the electrodes of the elliptic lamps, manufacturers usually request users not to tilt the projector apparatus over a certain angle β (normally 20 degrees) upward or downward as shown in FIG. 3C. when in use to avoid high temperature and damage to the electrodes. More specifically, if the projection lens 16 are tilted up or down over a certain degree β, as shown in FIG. 3C, one of the lamps may go beyond a critical point of safety and overlaps with the high temperature region 18. This is a possible serious defect to the lamps 11, 12 only under a relatively short period of operating time.
In order to enhance performance and extend the life cycle of the dual light sources in the DLP projector apparatus, it is necessary to redesign a projector apparatus and a light coupling module thereof both adopted by a projector system with a single light source or multi-light sources.